Wax compositions



United States Patent 3,092,506 WAX COMPOSITIONS Anna M. Shadan, PoncaCity, Okla., assignor to Continental Oil Company, Ponca City, Okla., acorporation of Delaware No Drawing. Filed July 26, 1960, Ser. No. 45,293Claims. (Cl. 106-270) This invention relates .to wax compositions usefulin surface coating applications generally and especially adapted for thecoating or lining of paper containers and the like wherein comestiblesare temporarily stored. More particularly, this invention concernsparaffin wax compositions containing a minute amount of an oilsolublepetroleum sulfonate soap which compositions in the molten or fluid stateexhibit improved non-foaming tendencies. The present invention furtherrelates to a process for preparing said wax compositions.

Because of their outstanding resistance to water and overall excellentchemical resistance and inertness, waxes are extensively utilized tocoat paper containers designed for packaging comestibles. Probably themost notable example of an application of this type is exemplified inthe packaging of dairy products, particularly milk. In carrying out thecoating procedure, it is customary to dip a fiat blank of the cartoncontainer into a molten bath of the wax and thereupon shape the blankafter the wax deposit has suitably solidified.

Most waxes, irrespective of their source or origin, exhibitobjectionable foaming tendencies in the molten state, especially whenliquid baths therof are subjected to the degree of mechanical agitationnormally occurring in the various coating operations. Generally, thecharacter of the foam encountered in molten Wax compositions issufficiently stable so that when the wax solidifies on the surface ofthe paper there results portions thereof having thin or otherwiseinadequate covering of the wax. If these faulty areas are'on the surfaceforming the inside of the container, it is likely that the liquidcontents will ultimately penetrate the paper at these areas therebyweakening the paper to the extent that leakage develops. On the otherhand if the foam covers the outside of the container, the functionalpurpose of the container may not be adversely affected but neverthelessin many of such instances the containers have to be disposed of asrejects because of their unattractive appearance.

In current commercial wax coating practices of the type hereinabovementioned a petroleum, and more specifically, a paraflin wax is favoredsince this type of wax is readily available and comparativelyinexpensive. This invention, however, is not limited to the use of apetroleum wax but can be beneficially utilized to inhibit the foamingtendencies of other type waxes and mixtures thereof with a petroleumwax.

One of the principal objects of the present invention is to provide anon-foaming wax composition.

Another object of this invention is to provide a paraflin waxcomposition containing a small but efiective amount of an oil-solublesodium salt of a petroleum sulfonate capable of rendering saidcomposition substantially nonfoaming in nature when existing in a moltenstate.

Other objects and advantages of this invention will become more apparentto those skilled in the art upon a consideration of the detaileddiscussion and example set forth hereinbelow.

Since paraffin wax or a wax composition containing a major portion ofparafiin wax is viewed as the preferred composition in the practice ofthis invention, a mention will be made here to the various grades andtypes coming within the scope of the term parafiin wax as contemplatedherein. This can be best accomplished by briefly considering theprocedures ordinarily involved in producing a parafiin wax.

Parafiin waxes are the wax constituents occurring in various fractionsof certain crude petroleums. They manifest melting points in a range ofabout 47 to 65 C. and Saybolt viscosities in the range of from about 35to 45 S.U. at 210 F., and are further physically characterized bycrystallizing into large, well-formed distinct crystals of the plate andneedle types. The precise physical characteristics of a paraflin wax mayvary depending upon the crude source, the portion of the crude used forwax production and differences in refining techniques.

In the preparation of paraflin wax, a crude petroleum stock having sucha wax constituent is subjected to fractional distillation whereby cutsare obtained ranging from heavy gas oil to heavy lubricating oil. Thelight fractions or cuts are the richest in wax components andaccordingly are usually termed parafiin or wax distillates. Theseparaffin rich fractions are normally liquid at to F., whereas coolingbelow this range readily effects precipitation of the wax. This limitedsolubility characteristic at low temperatures is availed of to segregatemost of the wax content. The precipitate is then filtered by any ofseveral conventional methods in a process termed pressing which processyields a filtrate called slack wax. Slack wax normally contains fromabout 20 to 40% oil content. Subsequent to the pressing operation, theslack oil is sweated. Sweating is accomplished by heat treating theslack wax whereby the oil will drain or sweat out of the solid wax asthe temperature is slowly raised. The sweating operation yields a crudescale wax containing about 2% oil and melting at about 122124 F. Fullyrefined paraffin wax is then obtained by merely further sweating thecrude scale wax to a specific melting point range followed by treatmentwith a suitable adsorbent such as fullers earth, bone char, bauxite andthe like. The fully refined product is substantially free of oil.

The use of the highly refined type of paraffin wax is not mandatory inthe various coating operations mentioned hereinabove. Thus, mixtures ofthe refined product with slack wax or crude scale wax may beadvantageously employed. Furthermore, substantial amounts of other waxmaterials may be incorporated in the paraffin wax in order to obtaincertain desired properties relating to tensile strength, meltcharacteristics, etc. For example, the parafiin wax can be mixed withsynthetic materials such as the wax-like amorphous polyethylenes orpolypropylenes, pentaerythritol esters, and the like. Additionally,waxes of animal or vegetable origin can be similarly used, e.g.,beeswax, carnauba wax, etc. Also, microcrystalline waxes can beadvantageously used in combination with parafiin wax.

It is also contemplated that non-wax additives can be included in theWax composition such as, for example, an anti-oxidant capable ofinhibiting any oxidation tendency of the wax or waxes present.

In view of the above, the term parafiin wax composition used herein andin the appended claims broadly contemplates those above-describedcompositions or mixtures having general utility in the coating arts.However, a prefer-red wax composition for practicing the presentinvention is one wherein the paraffin wax content is at least 50% of thetotal weight of the composition.

In accordance with the present invention, foaming tendencies of aparafiin wax composition can be substantially and in many instancescompletely eliminated by homogeneously incorporating thereintorelatively minute quantities of a sodium salt of an oil-soluble ormahogany sulfonate. I have found unexpectedly that a comparatively smallbut characterizable class of the aforesaid su-lfonates will effectivelystabilize a molten paraffin wax composition containing at least about50% paraffin wax against foam formation. Not only are these sulfonatesexcellent arresters of foaming tendencies in said environment but thechemical nature thereof and the small quantities needed in order tosecure beneficial stabilization are such which do not significantlyaffect the nontoxicity characteristics of the parafiin Wax composition.This obviously is very important since these wax compositions areextensively used to coat paper containers which ultimately come intocontact with food.

As indicated above, only a particular type of mahogany sul-fonate can beused effectively in the practice of this invention. There are severalWays of empirically classifying the diiferent mahogany sulfonatesgenerally available such as by average molecular weight, relativesolubility in oil, etc. However, there are considerable shortcomings tothis manner of defining the particular class of sulfonates useful hereinand accordingly it has been noted that the most satisfactory method ofcharacterizing these suitable sulfonates consists of specifying theparticular type or fraction of petroleum oil from which the presentsulfonates can be derived.

The ,sulfonates which I have found to be eifective antifoarnants forparatlin wax compositions are those oilsoluble products obtained bysulfonating a petroleum oil fraction having a viscosity between about 80and 120 Saybolt Universal seconds at 100 F. The preferred sulfonates arethose derived from a petroleum fraction having a viscosity of about 100SUS. Suitable fractions can be obtained from any of the parafiinic,naphthenic, or mixed base crudes. Depending on the particular type ofcrude source used to obtain this fraction, it may be desirable to varythe sulfonation procedure. Thus, the conventional procedure is used whenemploying a parafiinic base crude, namely, of solvent refining the crudeemploying only one solvent extraction step and thereupon sol-fonatingthe raffinate. In other instances where a fraction is employed which hadbeen obtained from a crude containing a high content of aromaticity, itis generally desirable to treat the fraction with two or more solventextraction steps before subjecting the final raffinate to a sulfonationprocedure. The solvent refining step or steps facilitate separation ofexcessive amounts of the aromatic hydrocarbons from the lubricating oilfraction which hydrocarbons if allowed to remain complicate recovery ofthe desired sulfonates. The various types of extracting agents which canbe used are such as furfu-ral, liquid sulfur dioxide, etc. Ordinarilyfurfural is preferred as the solvent extracting agent.

In snlfonating the ratfinate any of the conventional sul fonating agentsand techniques can be used. Suitable amoung the sulfonating agents are:concentrated'su-lfuric acid, fuming sulfuric acid (oleum), sulfurtrioxide, chlorosulfuric acid, etc. Fuming sulfuric acid compositionscontaining from about 10 to 50% by weight excess S represent thepreferred sulfonating agents.

' Sulfon'ation temperatures are usually controlled within the range ofabout 50 to 200 F. with the preferred operating range being betweenabout 80 and 160 F. The oilacid weight ratio varies with the sulfonationtemperature, the extent to which the lubricating oil fraction has beenrefined, etc., but generally is in the range from about 1.5

to 6 when using the preferred sulfonating agents.

The sulfonation step produces two principal types of sulfonationproducts. One type, termed green acids, are water soluble and settle outof the sulfonation reaction system as a sludge. The desired oil solubleor mahogany sulfonates remain in the oil phase and are appropriatelyrecovered for the purposes herein by neutralizing the dissolved acidswith sodium hydroxide and then extracting the resulting salts by meansof a dilute aqueous solution of an alcohol such as isopropanol.

The amount of the oil-soluble sodium sulfonate which can be used inorder to stabilize parafiin Waxes against foam formation in accordancewith this invention is a variable and ranges from about 0.01 to 0.1%based on the weight of the wax composition. Quantities greater than 0.1%can be used to attain foam stabilization, however, the use of amountssignificantly greater than this stated maximum figure may cause acondition of blistering when a paper substrate is coated with a waxcontaining such amounts of the sodium sulfonate. A preferred amount ofsulfonate ranges between about 0.02 and 0.05% based on the weight of thewax composition.

Various ways can be employed to effectively incorporate the instantanti-foamants into the wax composition. The sul-fonate can beincorporated directly into the molten wax by means of a high speedstirrer or similar device. However, because of the high viscosityassociated with the instant sulfonates, it is preferred to blend samewith a white mineral oil and thus incorporate these mixtures into themolten wax composition. Using this mode of incorporation, applicableratios of sulfonate to white mineral oil can vary from about 7:3 to 1:9,respectively.

In order to further illustrate the nature of the present invention thefollowing example is given in which all parts or percent figures are byweight. It is to be understood that this invention is not limited to thespecific details set forth in this example except that such limitationsare expressed in the appended claims.

EXAMPLE I This example illustrates the effectiveness of a sodium salt ofa mahogany sulfonate obtained from a petroleum oil having a viscosity ofabout SUS as an anti-foaming agent for a wax composition. The wax usedin the series of :tests outlined below was a parafiin wax having amelting point of about 127-128 F. modified with 15% of amicro-crystalline Wax.

A specimen of standard stock paper used to prepare milk cartons wasprovided with a coating of wax by immersing the paper within a bath ofthe molten wax. Upon withdrawing the specimen and solidification of theapplied coating the specimen was noted for uniformity of coating andrated accordingly. These ratings were based on numerical value given ona demerit scale rang ing from zero to eight. In this particular systemof rating, seven indicates an excessive amount of faults due to foam. Onthe other hand, a rating of zero indicates that the coating issubstantially free of any irregular portions attributed to the presenceof foam within the coating bath. In general, ratings of four or lessindicate that the coating is acceptable.

Additionally each of the tests includes a rating for blistering which isset forth as being either satisfactory or unsatisfactory.

The composition of the various wax coating baths together with therespective ratings noted therefor are set forth in the following TableI. In all tests, with the exception of the control and that identifiedas coating F, the anti-foaming agent was incorporated into the moltenwax as a dispersion of the soap in white mineral oil in the ratio of7:3, respectively.

1 Sodium salt 0! a mahogany sulionate having a M.W. of about 435obtained from a solvent extracted lube oil fraction of 100 SUS at 100 F.

1 Contains 1% added white mineral oil.

I claim: 1. A parafiin wax composition stabilized against foam formationin the molten state consisting essentially of a paraffin wax containinga homogeneous dispersion of a small but effective foam inhibiting amountof a sodium salt of a mahogany sulfonate obtained by contacting apetroleum oil fraction having a viscosity between about 80 and 120 SUSat 100 F. with a sulfonating agent.

2. A parafin wax composition stabilized against foam formation in themolten state consisting essentially of a parafiin wax containing ahomogeneous dispersion of from about 0.01% to 0.1% of a sodium salt of amahogany sulfonate obtained by contacting a petroleum oil fractionhaving a viscosity between about 80 and 120 SUS at 100 F. with asulfonating agent.

3. A paraflin wax composition stabilized against foam formation in themolten state consisting essentially of a paraffin Wax containing ahomogeneous dispersion of from about 0.02% to 0.05 of a sodium salt of amaliogany sulfonate obtained by contacting a petroleum oil fractionhaving a viscosity between about 80 and 120 SUS at 100 F. with asulfonating agent.

4. A parafiin wax composition stabilized against foam formation in themolten state consisting essentially of a paraffin wax containing ahomogeneous dispersion of -ron1 about 0.01% to 0.1% of a sodium salt ofa mahogany s-ulfonate obtained by contacting a petroleum oil fractionhaving a viscosity of about 100 SUS at 100 F. with a sulfonating agent.

5. A paraflin wax composition stabilized against foam formation in themolten state consisting essentially of a parafiin wax containing ahomogeneous dispersion of from about 0.02% to 0.05% of a sodium salt ofa mahogany sulfonate obtained by contacting a petroleum oil fractionhaving a viscosity of about 100 SUS at 100 F. with a sulfonating agent.

6. A p arafiin wax composition comprising at least about 75% paraffinwax, said composition containing a homogeneous dispersion of from about0.02% to 0.05% of a sodium salt of 1a mahogany sulfonate obtained by 6contacting a petroleum oil fraction having a viscosity between about 80and 120 SUS at 100 F. with a suitenating agent.

7. A parafiin Wax composition comprising at least about paraffin wax,said composition containing a homogeneous dispersion of from about 0.02%to 0.05% of a sodium salt of a mahogany sulfonate obtained by contactinga petroleum oil fraction having a viscosity of about 100 SUS at 100 F.with a sulfonating agent.

8. A process for stabilizing a paraffin wax composition against foamformation in the molten state comprising uniformly admixing with saidcomposition from about 0.01% to 0.1% of a sodium salt of a mahoganysulfonate obtained by contacting a petroleum oil fraction having aviscosity between about and 120 SUS at F. with a sulfonating agent.

9. A process for stabilizing a paraflin wax composition against foamformation in the molten state comprising uniformly admixing with saidcomposition from about 0.02% to 0.05 of a sodium salt of a mahoganysul-fonate obtained by contacting a petroleum oil fraction having aviscosity of about 1-00 SUS at 100 F. with a sulfonating agent.

10. A process for stabilizing a paraffin wax composition containing atleast about 75 parafiin Wax against foam formation in the molten statewhich comprises uniformly admixing with said composition from about0.02% to 0.05% of a sodium salt of a mahogany sulfonate obmined bycontacting a petroleum oil fraction having a viscosity between about 80and SUS at 100 F. with a sulfonating agent.

References Cited in the file of this patent UNITED STATES PATENTS

1. A PARAFFIN WAX COMPOSITION STABLIZED AGAINST FOAM FORMATION IN THEMOLTEN STATE CONSISTING ESSENTIALLY OF A PARAFIN WAX CONTAINING AHOMOGENEOUS DISPERSION OF A SMALL BUT EFFECTIVE FOAM INHIBITING AMOUNTOF A SODIUM SALT OF A MAHOGAN SULFONATE OBTAINED BY CONTACTING APPETROLEUM OIL FRACTION HAVING A VISCOSITY BETWEEN ABOUT 80 AND 120* SUSAT 100*F. WITH A SULFONATING AGENT.